The present invention relates generally to a contour cutting machine, more particularly for cutting foam material in vertical direction.
A vertically cutting machine for cutting foam materials as disclosed in German patent specification no. 3,444,612 has a holder or cutting unit carrier which is of a generally C-shaped configuration. The mouth of the opening defined between the limbs of the C-shape is bridged across by a running-around cutting member in the form of a milling cutting wire or a heating wire, extending through a slot in a horizontal support surface of the workpiece table and producing a gap according to the thickness of the wire. The cutting wire can be displaced lengthwise in the slot so as to cut through material which is carried and supported on the surface of the workpiece table which comprises two separate feed elements for moving the workpiece transversely with respect to the direction of displacement of the cutting member in the slot, so that it is possible generally to cut curves or contours in the workpiece material such as foam from which shapes are to be cut. More specifically, the support surface of the workpiece table comprises two endless belts which are adjacent and so are forming a generally funnel-shaped slot. The belts can be driven in the same direction in order to move a workpiece supported thereon in one direction or the other, against the resistance of the cutting wire. Since the gap produced is a milled or melted gap between the cut pieces of material such cut pieces can move towards each other about the width of the gap. In addition, in operation of the machine, the endless belts which support the workpiece have a tendency occasionally to move laterally. Those two phenomena mean that the contours cut by the machine may be shifted from the location at which they are desired to be produced, thus giving rise to inaccurate cutting.
In addition, when dealing with samll foam pieces, there is the problem that the friction of the foam against the endless belts is too low relative to the necessary cutting pressure so that there is a danger of the foam material slipping, with the result that the curve which is cut in the foam material is defective. If the cutting wire pulls the foam piece which has been cut thereby towards the generally funnel-shaped slot between the two endless belts, that gives rise to the risk that the belt may pull the cut piece of foam material into the slot, thus also resulting in defective cutting. If on the other hand the wire is displaced in a direction such that the material to be cut is lifted away from the surface on which it is supported on the workpiece table, then it is no longer possible to achieve the necessary cutting pressure, transversely with respect to the workpiece, and it is then not possible to cut a curve.
A contour cutting machine as disclosed in German patent specification no. 3,313,133 provides that the cutting member is in the form of a horizontally extending and oscillating band blade knife and is of a length which only slightly exceeds the cutting region above the workpiece table. The band blade knife is gripped between two clamping devices which are rotatable by motor means to turn the knife according to the contour to be cut and which are simultaneously driven to oscillate the knife in its longitudinal direction. The clamping devices are located in a cutting unit carrier which can be moved up and down on the main frame structure of the machine and therefore also the knife. The workpiece can be moved in a horizontal direction by means of the workpiece table. It is thus possible to provide for relative displacement of the workpiece with respect to the knife along two axes. The knife is always turned so as to face in the desired direction of cut so that it is possible to cut curves or contours which f. i. appear on the vertical side surfaces of a foam block.